Based on customer feedback: The generated URLs for stylesheets are not human readable. It would be nice if the names are nice and human readable e.g. like with CDN enabled true.
Based on customer feedback: At times customers need both CDN enabled and combined styles. Since it's impractical to have all possible combinations ready on the CDN, a per skin combination sounds more reasonable. I.e. Default.all.css or something similar. That's for CDN. When running StyleSheetManager locally, again bundling (or defining groups) is a nice addition, as it allows a more specific manner. Of course such explicit feature, should and must negate the effect of counting selectors and splitting files.
Under heavy load in a multithreaded environment, a concurrency issue can occur, related to System.Collections.Generic.Dictionary`2.Insert
This might lead to High CPU usage and might require an IIS restart.
Currently the RadStylesheetManager renders embedded styles below user defined styles. In terms user defined cascades are overridden and developers need to use stronger selectors. Adding the ability to control where the embedded stylesheets are rendered will solve this and other issues.